1. Field of the Invention
The present invention relates to a network system for connecting to the Internet by utilizing an Internet service provider, a router to be used in the network system, a host to be used in the network system, a prefix management method for the router, and an IP address management method for the host.
2. Description of the Related Art
In recent years, the utilization of the world largest computer network “Internet” has been spreading, and new computer businesses have been developed by accessing the Internet and utilizing disclosed information or services, or by providing information or services to external users who make accesses through the Internet. Also, new technological developments regarding the Internet utilization have been in progress.
On the Internet, each computer has an identifier called IP address, and the packet exchanges are carried out according to this IP address.
In IPv6, a mechanism called Address Auto Configuration is provided such that each device can autonomously set up the IP address without any human manual operation. In this mechanism, basically, a router notifies a prefix of an address managed for each interface of that router to a link by the multicast or broadcast, and each node listens to this and concatenate an interface address of that node.
Now, when a computer and the other devices of each home are constantly connected to the Internet, an IP address (global address) will be allocated fixedly to a computer or the like of each home. Then, this IP address is most likely (in principle) changed only in units of a very long period of time, such as a period until the connection target provider of the home is changed, for example, if it is ever changed. Also, the IP address is an indicator of a location on the network, so that it is preferable to have this location indicator unchanged from a viewpoint of the service providing side.
For example, consider the case where the video data are stored in a video deck connected to a home network (A) of some home and it is desired to reproduce them on a video data reproduction device connected to a home network (B) of another home through the Internet. In this case, one possibility is to treat the video deck on the home network A side as a service providing side. In this case, at the home network B side, the video data reproduction device will be commanded to receive the video data from the video deck on the home network A side. In this regard, the video data reproduction device on the home network B side needs to learn the IP address of the video deck on the home network A side (in the case of using end-to-end communication). On the other hand, another possibility is to treat the video data reproduction device on the home network B side as the service providing side. In this case, the video deck on the home network A side will be commanded to transmit the video data to the video data reproduction device on the home network B side. In this regard, the video deck on the home network A side needs to learn the IP address of the video data reproduction device on the home network B side.
However, if the IP address of the correspondent is changed frequently, it would become necessary to have a special mechanism or a human manual operation in order for the service providing side to learn the IP address of the correspondent. The same problem also arises in the Internet telephone because the call originating side of the Internet telephone needs to learn the IP address of the call terminating side.
As such, it is preferable to utilize the same IP address for a sufficiently long period of time such that it can be regarded as not changing, and this is most likely be the case in practice.
However, when the same IP address is utilized for a long period of time, there is a drawback that the serious problem of the privacy violation can possibly occur. Of course, the communication content itself can be concealed by encrypting it. However, it is basically difficult to encrypt the IP address. For this reason, it is possible to ascertain the correspondents of one user or the web site browsing preference of one user, by eavesdropping communications on a communication path, taking statistics of the IP addresses obtained by the eavesdropping, and analyzing them. Such information regarding the existence of the communication itself or information regarding correspondents can be used for the serious privacy violation.
As a conventional mechanism for protection against the privacy violation due to the IP address leakage, Privacy Extensions for Stateless Address Autoconfiguration in IPv6 (RFC 3041) is available. In this mechanism, the identification of the same device by the IPv6 address is made difficult by periodically changing a portion corresponding to the interface ID in the IPv6 address.
However, under the environment in which each home is constantly connected to the Internet, this mechanism cannot resolve the problem. This is because in the environment such as the home, the identification of the sub-network is considered as most problematic, but this mechanism only makes the identification of the device belonging to one sub-network difficult, so that under the environment in which each home is constantly connected to the Internet, the identification of the sub-network is still possible.
As such, the conventional mechanism has been impossible to protect the privacy in units of the sub-networks. Thus, it has been impossible conventionally to prevent the privacy violation by acquiring the personal information according to the IP address obtained by eavesdropping communications.